We are building a 2500 sq ft house in Oregon (pretty mild climate - rarely goes below 30 F, about a constant 40 something F in the winter).  I am looking for suggestions for the most efficient, least polluting form of wood heat.  We have an abundance of wood on the land, and we don't want to require fossil fuels or the grid for our heat source.  We're considering radiant floor heat with an indoor wood boiler, but I've heard that emmisions can be a problem.  Any suggestions?

Several companies are making wood burning water stoves, that is what i would look into. In fact i' am looking into that for my house, and using radiant heat, heating my potable hot water, and a hot tub.

Do you have any links to companies that are making these? I know that you can make them yourself - I haven't run across any that are pre-fab.
Thanks for your input!

my research led me to this company that best fits your description:

 

http://www.woodboilers.com/

I agree with Tim.

The BioHeat boilers are amazing and produce virtually no emissions at all.

the whole lineup is pretty impressive but the most impressive cord wood boiler I've ever seen is the Frohling turbo. We heat our shop and office with one and it is so incredibly easy to use and to fire and so clean, it is amazing.

http://www.woodboilers.com/product-detail.aspx?id=50

good luck

~Fortunat

Most of the wood boilers are WAY oversized for the heat load of a reasonably tight & insulated house that size in a climate where the design temperature is in the mid-20s & up. Odds are pretty good that the heat load of your place is well under 20KBTU/hr when it's 30F out- even the smallest Tarm Multi-Heat pellet boiler is over 50K max, but it's minimum continuous output is 15.7k- probably reasonably close to your design-day load. If you have ready access to pelletized fuel at a reasonable price it might not be a bad choice.

http://www.woodboilers.com/product-detail.aspx?id=54

The smallest Froling Turbo cordwood-burner has an output of 70KBTU/H. The only reasonable way to deal with the oversizing is a large amount of thermal storage (a big tank full of very hot water), which adds to the upfront cost. Going with less storage and shorter, more frequent burns may keep you warm, but the average efficiency goes down, and frequent cycling puts wear on the boiler.

You'll need some amount of storage with either type of system, but the greater the oversizing, the more storage capacity is called for. Large unpressurized tanks are cheaper, but running at atmospheric pressure allows oxygen to get into the system, which corrodes the boiler's heat exchangers as well as the system pumps, which is why they come with multiple in-tank heat exchangers.

For the types of heat loads you're talking, a small wood stove running ~70% efficiency is a lot cheaper up front, but it won't run hydronic floors, heat your domestic hot water, and would need a somewhat open floor plan for it to comfortably heat the whole house.

As it's new construction, it's useful to look at the big picture and compare the expense of going with a complex heating system vs. super-insulating PassivHaus style. What it takes to go PassivHaus in SW OR is a lot less than what it takes in colder areas. Sufficiently insulated "heating mode" in a climate that mild could mean as little as switching the ventilation from direct vent to heat-recovery mode, or changing the ventilation rate.

just posted this suggestion elsewhere, but look at www.woodheat.org it's EXHAUSTIVE and goes into boilers, fireplaces, woodstoves, harvesting, seasoning, splitting technique, gloating ideas for dinner parties . . . you get the idea.

If I were building new, I'd seriously think about a masonry heater. Bear in mind I have NO idea what the upfront costs are, but if you're interested in going passive solar, the mass of the masonry heater can also serve as thermal mass to store solar energy! The idea behind them is to enclose a small firebox in a massive block structure. The fires are small and efficient (super clean), and the heat is captured by the block to be radiated back slowly into the room. Seems like it would solve some of the modulation issues people experience with traditional woodstoves.

good luck!
charlie